coinor-osi fails to build from source on arm64 (but did succeed before)

seen in a segfault running the tests in the coinor-osi package,
https://launchpad.net/bugs/1263576, both in saucy and trusty, version 0.106.4
and 0.106.5. Version 0.103 doesn't show the issue.

both the 4.7 and 4.8 linaro branches show this behaviour, and trunk 20131121
(didn't build a newer one yet).

William Grant tracked that down to a bug with very negative vcall_offsets in
aarch64 multiple inheritance thunks. The example below has two consecutive
thunks, with the second adding 263 instead of subtracting 264.
aarch64_build_constant seems to not handle negative integers. He tried a quick
gcc patch to avoid using aarch64_build_constant, and the coinor-osi tests succeed.

0000000000401ca4 <_ZTv0_n256_N1C2adEv>:
  401ca4: f9400010 ldr x16, [x0]
  401ca8: f8500211 ldr x17, [x16,#-256]
  401cac: 8b110000 add x0, x0, x17
  401cb0: 17fffff9 b 401c94 <_ZN1C2adEv>

[...]

0000000000401cc4 <_ZTv0_n264_N1C2aeEv>:
  401cc4: f9400010 ldr x16, [x0]
  401cc8: d28020f1 mov x17, #0x107 // #263
  401ccc: f8716a11 ldr x17, [x16,x17]
  401cd0: 8b110000 add x0, x0, x17
  401cd4: 17fffff8 b 401cb4 <_ZN1C2aeEv>

Any chance for a quick 2013 review?

Thanks, Matthias

--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -2540,8 +2540,8 @@
    addr = plus_constant (Pmode, temp0, vcall_offset);
       else
  {
- aarch64_build_constant (IP1_REGNUM, vcall_offset);
- addr = gen_rtx_PLUS (Pmode, temp0, temp1);
+ aarch64_add_constant (IP0_REGNUM, IP1_REGNUM, vcall_offset);
+ addr = temp0;
  }

       aarch64_emit_move (temp1, gen_rtx_MEM (Pmode,addr));

I think the actual issue is with the code in aarch64_build_constant:

      /* zcount contains the number of additional MOVK instructions
  required if the constant is built up with an initial MOVZ instruction,
  while ncount is the number of MOVK instructions required if starting
  with a MOVN instruction. Choose the sequence that yields the fewest
  number of instructions, preferring MOVZ instructions when they are both
  the same. */
      if (ncount < zcount)
 {
   emit_move_insn (gen_rtx_REG (Pmode, regnum),
     GEN_INT ((~val) & 0xffff));
   tval = 0xffff;
 }
      else
 {
   emit_move_insn (gen_rtx_REG (Pmode, regnum),
     GEN_INT (val & 0xffff));
   tval = 0;
 }

The GEN_INT in the first if branch is incorrect as it truncates the immediate at 16-bits, and so we will never generate the "MOVN" form. What it should be instead is: GEN_INT (~((~val) & 0xffff)) or equivalent.

Author: clyon
Date: Wed Jan 15 10:27:55 2014
New Revision: 206628

URL: http://gcc.gnu.org/viewcvs?rev=206628&root=gcc&view=rev
Log:
2014-01-15 Matthew Gretton-Dann <email address hidden>
            Kugan Vivekanandarajah <email address hidden>

 gcc/
 PR target/59695
 * config/aarch64/aarch64.c (aarch64_build_constant): Fix incorrect
 truncation.

 gcc/testsuite/
 PR target/59695
 * g++.dg/pr59695.C: New testcase.

Added:
    trunk/gcc/testsuite/g++.dg/pr59695.C
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/config/aarch64/aarch64.c
    trunk/gcc/testsuite/ChangeLog

Author: clyon
Date: Fri Jan 17 11:05:04 2014
New Revision: 206703

URL: http://gcc.gnu.org/viewcvs?rev=206703&root=gcc&view=rev
Log:
2014-01-17 Kugan Vivekanandarajah <email address hidden>

 gcc/
 Backport from mainline
 2014-01-15 Matthew Gretton-Dann <email address hidden>
            Kugan Vivekanandarajah <email address hidden>

 PR target/59695
 * config/aarch64/aarch64.c (aarch64_build_constant): Fix incorrect
 truncation.

 gcc/testsuite/
 Backport from mainline
 2014-01-15 Matthew Gretton-Dann <email address hidden>
     Kugan Vivekanandarajah <email address hidden>

 PR target/59695
 * g++.dg/pr59695.C: New testcase.

Added:
    branches/gcc-4_8-branch/gcc/testsuite/g++.dg/pr59695.C
      - copied unchanged from r206628, trunk/gcc/testsuite/g++.dg/pr59695.C
Modified:
    branches/gcc-4_8-branch/ (props changed)
    branches/gcc-4_8-branch/gcc/ChangeLog
    branches/gcc-4_8-branch/gcc/config/aarch64/aarch64.c
    branches/gcc-4_8-branch/gcc/testsuite/ChangeLog

Propchange: branches/gcc-4_8-branch/
            ('svn:mergeinfo' modified)

Fixed now presumably.